Grinding-bur.



J. H. LETZ.

GRINDING BUR.

APPLICATION HLED FEB. 7, 191s.

1 1 8 1,123 1 Pa'fql-lted May 2, 1916.

- Burs, of which the fo trally receiving aperture, so that the gen- JOHN I-IQEIIAND LETZ, 0F CROWN POINT, INDIANA, ASSIGNOR TO THE LETZ MANUFAC- TURING COMPANY, OF CROWN POINT, INDIANA, A CORPORATION OF INDIANA.

GRINDING-BUR.

Specification of I-.etters Patent. Patented Misty 2, 11.916..

Application led February 7, 1916. Serial No. 76,506.

l to grind off the rough4 outer edges of the cast ribs into a series of perfectly flat surfaces, all lying in the same plane.

By reference to the various figures, it will be obvious that the ribs are arranged in groups in which the same design is repeated, each group covering a certain number of degrees, for instance, 30, of the entire surface of the disk. In the configuration of the aforesaid Letz Patent No. 437,699, each group of ribs is made up of a plurality of main ribs with short opposed branches extending therefrom, the main ribs of a group successively decreasing in length and the branch ribs projecting into the paths formed by the parallel main portions of the ribs to forma tortuous passage for the grain from the center to the periphery of the disks. As indicated in Fig. 2, the ribs on the two burs, when placed in juxtaposition, extend substantially across each other at right angles, and as the moving bur is rapidly rotated, the material fed between them passes by the centrifugal action out through the tortuous passages thus formed, and is discharged from the peripheries of the burs. The passages formed by the ribs lill up with the grain, and any grains or-particles Wider than the depth of the passages are sheared 0E by the cutting edges of the ribs as they pass each other.

Referring now especially to Figs. 1 and 2, the set of ribs corresponding to a long rib and its branches of the bur of the aforesaid LetZ Patent No. 437,699, consist of three main ribs l, 2a, and 3, and three smaller ribs 4a, 5a and 6a. vThe main ribs l:L and 2 will bev seen to consist of the inner portion which extends at an acute angle to an adjacent radial line, and of an outer portion which extends substantially parallel to said radial line. The ribs ta and 3a will be seen to constitute continuations, as it were, of the line formed by the inner portions of the ribs 1a and 2a. The ribs 5a and 6a will be seen to extend away substantially at right angles to the angles of 'the ribs 41a and 2, being separated therefrom, as shown. This general design corresponds to a long rib and its branches of the aforesaidv Letz Patent No. 437,699, if sections were cut out therefrom. at the points where the branches occur. Similarly, the ribs 1b, 2b, 4b, 5b and 6b correspond to the To all whom t may concern: A

Be it known that I, JOHN HOLLAND Ln'rz, a citizen of the United States, and a resident of Crown Point, in the county of Lake and State of Indiana, have invented certain new and useful Iiopror'nnents in Grindingwing is a full, clear, and exact specification. l My invention is l:oncerned with improvements in grinding burs of the type shown in the Letz Patent No. 437,699, dated October 7, 1890, in which a disk having a generally fiat face has formed thereon a series of main ribs from which shortopposed branch ribs diverge at intervals, the tops of said ribs being ground flat and serving as cutting or shearing edges when coperating with the similar ribs of the companion bur in grinding grain or other materials.

My invention consists in a change in the configuration of the ribs, whereby the capacity of the grinding mill employing them can be increased, and the amount of friction reduced.

To illustrate my invention, I annex here' to a sheet of drawings in which the same reference characters are used to designate identical parts in lall the figures, of which` Figure l is.a plan View of a section of a bur embodying my invention; Fig. 2 is a similar View of a larger section with portions of the companion bur superposed thereon to indicate the relationship of the ribs; and Fig. 3 is a cross-section on a large scale on the line 3-3 of Fig. 1.

As these burs are ordinarily constructed, the stationary bur, at any rate, has a ceneral shape of the bur is that of an annulus. As seen in cross-section in 3, this annulus consists of a body portion a, the upper surface of which is generally fiat, although it is preferably slightly inclined at b on the interior -of the grinding surfaces. I may employ a pair of annular flanges c onthe reverse face, but my invention is concerned with the design of the ribs which' are shown as raised a Slight distance above the flat surface of the part a, and as having their upper surfaces ground off flat, so as to form shearing edges. It will, of course, be understood that these burs are preferably formed by casting them, and that after they are cast, it is an extremely simple opera-tion next shorter rib and its branches of the aforesaid Lotz patent, with the saine sections removed. Likewise, the ribs l, 2, 40,' .3 and (5 correspoinl to the next shorter rib and its branches of the original Lotz patent., and so on. 1With. this new configuration of the ribs l find that the capacity of the mill is materially increased without destroying in the least the ineness of the grinding, this increased capacity' probably being due to the grain being free to pass in a 4incre nearly radial line between the burs by passing through the cut-away portions.

.ln the matter of reduced friction, I find that this is also very perceptible, and this reduced friction probably results from the reduction of the large triangular surfaces found in the original Lotz patent, where the branch ribs 'unite with the inain rib, and as the ribs are ground down in use, the. areas of these triangular surfaces increase, increasing the friction. lf/Vith so much of these large triangular surfaces cut away as occurs in the new construction, thisfriction is very materially reduced.

N hat l claim as new and desire to secure by .Letters Patent of the Unite(` States is l. A grinding bur consisting of a generallyiiat disk having a series of grinding ribs projecting therefrom and having their fiat top surfaces in the saine plane and forming shearing edges, said ribs consisting of a plurality of long angular ribs having their main and inner portions extending at acuto angles to adjacent radial lines and their outer portions turned substantially parallel to said adjacent radial lines, and a corresponding plurality of short'ribs separated freni the long ribs and extending away from the angles of the long ribs, substantially at right angles to the outer 'portions thereof.

2. A grindingbur consisting of a generally flat dish; having a seriesof grinding ribs projecting therefrom, and having their flat top surfaces in the saine plane and forming shearing edges, said ribs consisting of a plurality of iong angular ribs having their inain and inner portions extending at acute angles to adjacent radial lines and their outer portions turned substatitially parallel to said adjacent radial lines, and a corresponding plurality of short ribs separated froni the long ribs and extending away froni the angles of the long ribs, substantially at right angles to the outer p0rtions thereof, the main portions of pairs of the lng ribs being in alineinent but not touching, and said pairs being grouped with others that are parallel, substantially as shown and described.

3. A grinding bur consisting of a generally flat disk having a series of grinding ribs projecting therefrom and having their flat top surfaces in the saine plane and forming shearing edges, said ribs consist ing of a plurality of long angular ribs having their inain and inner portions extending at acute angles to adjacent radial lines and their outer portions turned substantially parallel to said adjacent radial lines, and a correspoinling plurality of short ribs eX- tending away froin the angles of the long ribs, substantially at right angles to the outer portions thereof.

ln witness whereof, l have hereunto set lny hand and allixed iny seal, this 3rd day of February A. '1). 1916.

JOHN HOLLAND [n s] 

